The injection molds currently in use typically comprise a cavity member having a hollow cavity and a core member which fits in the hollow cavity to define the molding chamber between them. The hollow cavity member and the core member are relatively movable by means of a hydraulic or pneumatic system between open and closed positions to define the molding chamber between them in the closed position, and also being capable of opening to remove the molded item, which generally is carried on the core as the mold opens.
In the molding of an item such as a bucket, the rim or other structure may project inwardly from the main portion of the bucket wall. In this circumstance, a collapsible core may be required, for example see Von Holdt patent application No. 781,131, filed Sept. 26, 1985, now U.S. Pat. No. 4,627,810 or Von Holdt U.S. Pat. No. 4,533,312. The collapsible mold cores disclosed in the above references utilize longitudinally slidable outer core members which move along an inner core member or core base between a molding porition and a collapsed position, to make it possible to remove a freshly molded bucket or other item having inwardly projecting members from the core while the core is in collapsed position.
Because the outer members of the collapsible core move longitudinally, conventional molds must open a substantial distance to permit the molded object to fall off of the mold core between the two parts. The opening distance must account for the outer sliding mold core members in their extended position, and also provide additional space to permit removal of the molded object. Such a distance can be very substantial, which of course increases the time required for the opening and closing operation. As a further disadvantage, the extra wide mold opening that is required by means of collapsible cores having longitudinally sliding members may require one to use a higher tonnage mold press to get the increased mold opening capacity, when otherwise a lower tonnage press, which is less expensive, might do perfectly well.
By this invention, a mold can be provided in which a reduced opening distance is required, even when used with a collapsible core that collapses in the longitudinal direction. Hence, the invention of this application may make it possible to use a smaller press, which of course is less expensive, while at the same time providing substantial time saving efficiencies to the molding process. It is frequently possible to reduce the mold cycle time by 25 percent in the manufacture of large buckets and the like through the use of this invention.